Research support would enable the applicant to commit his time on essentially a full time basis to the study of hormone-opiate-brain interactions in the regulation of parental behavior in mammals. The research proposed here focuses upon the interactions among endocrine, neural and behavioral events associated with pregnancy, birth and the nurturing of young. Specifically, the objective of the research is to delineate the causal relationships which exist among the steroidal milieu, prolactin secretion, the endogenous opioid systems, and maternal behavior using a rat animal model. In the first set of experiments the involvement of prolactin in the induction of maternal behavor is examined. Possible modes and sites of prolactin's behavioral actions are investigated. The second set of experiments addresses the involvement of opiates in the regulation of maternal behavior. Endogenous opiate concentrations in behavioral important CNS loci will be measured by radioimmunoassay during pregnancy and lactation. Next, to determine whether the steroidal induction of maternal behavior is opiate-mediated, CNS-opioid concentrations will be measured after treatment of inexperienced female rats with behaviorally effective and ineffective steroid treatments. Other studies will enable us to identify sites and possible mechanisms of opiate regulation of maternal behavior. In the final series of experiments we examine those neural, endocrine and neuroendocrine factors that regulate prolactin secretion in males. Experiments test whether the male exhibits specific endocrine and neuroendocrine responses to the presentation of young. The effects of steroid-priming, neural stimulation and behavioral inputs on circulating prolactin levels in males are measured. Finally, the possible "organizational" effects of androgen exposure during prenatal and postnatal development on the ability to process sensory information from young, integrate this information centrally, and show an endocrine response are examined in male and female rats. In total, these studies are designed to advance our understanding of those biological events that regulate and are regulated by parent-young interactions. During the course of proposed support the applicant would gain additional scientific training in the areas of cell biology, neuroanatomy, and primate behavioral endocrinology. In addition, the applicant would organize a symposium on the Regulation of Parental Care, the proceedings of which would be published as a text.